1. Field of the Invention
The present invention relates to an electric dust collector system. More specifically, this invention relates to the improvement In electrode portions.
2. Description of the Prior Art
There are two major functions of an electric collecting system: One is to charge dust particles in the air by a corona discharging which takes place between a discharge electrode and a discharge counter electrode, and the other is to collect such discharged dust particles. A needle-shaped electrode, a fine metal string pulled by a spring, or the like is employed as the discharging electrode in the charging portion (also referred to as ionizer) to improve the discharging capability. The dust collector portion (also referred to as collector) comprises a dust collector electrode and a dust collector counter electrode each disposed counter to the discharging portion at suitable intervals. A stainless plate, stainless foil or insulated high polymer film with conductive coating material applied on its surface is employed as the dust collector electrode. A voltage smaller than that applied between the discharge electrode and the discharge counter electrode is applied to between the dust collector electrode and the dust collector counter electrode.
To restore the dust collecting efficiency after each use of the electric dust collector system, it is necessary to wash the both electrodes.
There is concern, however, that spark discharge will occur between the edges of the dust collector electrode and the dust collector counter electrode, when the metal is used for the dust collector electrode, unless the distance between both electrodes or the applied voltage is accurately controlled. When used is the high polymer film with conductive coating material applied on its whole surface, the spark discharge may also occur in the edge of the film. When the conductive coating material is applied to the central part of the high polymer film instead of to the edge of the film, the width of the high polymer film becomes greater, thus causing the depth of the dust collector portion to also become greater.
According to the Unexamined Japanese Patent Publication No. 48-88554, a semiconductor film having 10.sup.5 -10.sup.11 .OMEGA..multidot.cm of resistivity on the surface is adhered to the substrate in order to avoid the spark discharge problem in the edge. However, in this case, there is concern that the adhered semiconductor film will be peeled off at the time of cleaning to restore the dust collecting power or will be peeled off by an abnormal discharge phenomenon.